波阻抗约束反演中的约束方法研究

Study of constraint methodology in constrained impedance inver sion

1. 西北大学地质学系,西安710069;2. 石油地球物理勘探局研究院,涿州072750

Department of Geology, Northwest University, Xi'an 710069

基于褶积模型的波阻抗反演技术,由于受地震子波带限性质的影响,对反演结果的高频信息不能进行合理的约束。要想反演出比较准确的波阻抗高频信息,必须施加合理的约束条件。利用测井资料与层位解释结果构造的常规约束条件,在井点是可靠的,但横向离开井点一定距离后,约束条件的误差就会很大,从而导致约束反演结果的错误。本文从约束反演方法的模型试算出发,提出的以声波测井资料的最大和最小速度、速度包络、中值滤波及速度差结合作为约束条件的新方法,可以有效地降低噪声对反演结果的影响,减少解的非唯一性,提高井点以外地震资料反演结果的可信度。

Impedance inversion technique based on convolutional model can not reas onably constrain high-frequency information of inversion result due to the infl u ence of seismic wavelet band limitation property. To invert for accurate high-f r equency information of impedance, reasonable constraint conditions are needed. T he conventional constraint condition constructed by using well log data and hori zon interpretation results is reliable in the vicinity of borehole, but its erro r may be large at a certain distance away from borehole. Therefore this cause in accurate constrained inversion results. Starting from the model trial computatio n of constrained inversion, this paper presents a new method which takes the max imal and minimal velocity, velocity envolop, mid-value filtering, and velocity c ontrast of acoustic log data as constraint condition. The method can effectively reduce the influence of noise on inversion result, decrease the nonuniqueness o f solution, and increase the creditability of seismic data inversion result in a reas away from borehole.